Texture and Dispersal of Sediments in the Panama Basin

Abstract

The Panama Basin in the eastern equatorial Pacific is bordered by the continental margins of Central and South America and by the Cocos and Carnegie Ridges. A series of banks divides it into an eastern and a western basin. The distribution patterns of the sediments are the product of complex interactions between biological productivity, dissolution of calcite at depth, influx of continental debris, and dispersal and reworking of sediments by deep currents. Detailed grain-size analyses provide insight into the reworking-dispersal portion of this system. The coarsest grain-size modes in the sand and coarse-silt range are concentrated on banks and ridges by winnowing, while the chaff is deposited on ridge slopes and in the western basin. Approximately one-half of the sediment in the deep western basin is the product of reworking. In contrast, the finest silt and clay modes have been dispersed by near-bottom currents and show transport of continental and fine biogenous material from the eastern to the western...